Construction of Monophosphine–Metal Complexes in Privileged Diphosphine-Based Covalent Organic Frameworks for Catalytic Asymmetric Hydrogenation,Journal of the American Chemical Society

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Construction of Monophosphine–Metal Complexes in Privileged Diphosphine-Based Covalent Organic Frameworks for Catalytic Asymmetric Hydrogenation
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2023-03-10 , DOI: 10.1021/jacs.2c11037
Zehao Zheng ₁ , Chen Yuan ₁ , Meng Sun ₁ , Jinqiao Dong ₁ , Yan Liu ₁ , Yong Cui ₁

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Privileged diphosphine ligands that chelate many transition metals to form stable chelation complexes are essential in a variety of catalytic processes. However, the exact identity of the catalytically active moieties remains ambiguous because the chelated metal catalysts may undergo rearrangement during catalysis to produce monophosphine–metal complexes, which are hard to isolate and evaluate the activities. By taking advantage of the isolation of two phosphorus atoms, we demonstrate here the successful construction of chiral monophosphine–Ir/Ru complexes of diphosphine ligands in covalent organic frameworks (COFs) for enantioselective hydrogenation. By condensation of the tetraaldehyde of enantiopure MeO-BIPHEP and linear aromatic diamines, we prepare two homochiral two-dimensional COFs with ABC stacking, in which the two P atoms of each diphosphine are separated and fixed far apart. Post-synthetic metalations of the COFs thus afford the single-site Ir/Ru–monophosphine catalysts, in contrast to the homogeneous chelated analogues, that demonstrated excellent catalytic and recyclable performance in the asymmetric hydrogenation of quinolines and β-ketoesters, affording up to 99.9% enantiomeric excess. Owing to the fact that the porous catalyst is capable of adsorbing and concentrating hydrogen, the catalytic reactions are promoted under ambient/medium pressure, which are typically performed under high pressure for homogeneous catalysis. This work not only shows that monophosphine–metal complexes of diphosphines can be catalytically active centers for asymmetric hydrogenation reactions but also provides a new strategy to prepare new types of privileged phosphine-based heterogeneous catalysts.

中文翻译：

在用于催化不对称氢化的特殊二膦基共价有机骨架中构建单膦-金属络合物

螯合许多过渡金属以形成稳定螯合络合物的特殊二膦配体在各种催化过程中必不可少。然而，催化活性部分的确切身份仍然不明确，因为螯合金属催化剂在催化过程中可能会发生重排，产生难以分离和评估活性的单膦-金属络合物。通过利用两个磷原子的分离，我们在此展示了在共价有机骨架 (COF) 中成功构建手性单膦-Ir/Ru 配合物的双膦配体，用于对映选择性氢化。通过对映体纯的 MeO-BIPHEP 的四醛与线性芳香二胺的缩合，我们制备了两个具有 ABC 堆叠的纯手性二维 COF，其中每个双膦的两个 P 原子被分开并固定得很远。因此，COF 的合成后金属化提供单中心 Ir/Ru-单膦催化剂，与均相螯合类似物相比，后者在喹啉和 β-酮酯的不对称氢化中表现出优异的催化和可回收性能，提供高达 99.9 % 对映体过量。由于多孔催化剂能够吸附和浓缩氢气，催化反应在常压/中压下得到促进，而均相催化通常在高压下进行。

更新日期：2023-03-10

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